What are amphisbaenians? What morphological adaptations do they have to aid in burrowing?

Amphisbaeinians are worm lizards. This is a group is highly specialized, and its burroowing form is neither like a worm nor a lizard but certainly are related to the latter. They are limbless and can move backwards and forwards. They have elongate, cylindrical bodies of nearly uniform diameter. Their skull is solidly built and specially shaped for burrowing through the soil.